Downloads default Scala Compilers
compile_package_jars requires several versions of the
scala compiler to work, this is to match Spark scala versions.
To help setup your environment, this function will download the
required compilers under the default search path.
download_scalac(dest_path = NULL)
The destination path where scalac will be downloaded to.
find_scalac for a list of paths searched and used by
this function to install the required compilers.